1. Field of the Invention
The present invention relates to a tone characteristic data preparing system for preparing tone characteristic data such as calibration data.
2. Description of Related Art
In conventional printing systems that are capable of performing relatively high-quality multi-level tone printing, color calibration is performed to allow density levels obtained on a printed matter produced by a printer to properly match input density levels that are included in image data originally supplied from an upper mark or superior program, such as an application program.
It is conceivable to prepare tone characteristic data or calibration data using a procedure described below.
It is now assumed that a printer is designed to be capable of performing color printing using four colors of ink, that is, cyan (C), magenta (M), yellow (Y), and black (K) ink, and to be capable of printing images in multi-level tones, 256 total tone levels, for example, for each color. During the calibration data preparing operation, the printer is controlled to produce a test chart by printing a plurality of color patches as shown in FIG. 1.
As shown in FIG. 1, each color patch is a pattern in an optional shape (square shape in this example) whose inner area is completely printed to a uniform tone. The color patches are printed in four rows, one row for each of the colors of cyan (C), magenta (M), yellow (Y), and black (K). In this example, each row includes nine color patches aligned in the row. The nine patches in each row are printed with nine different output tone levels that are separated by about 32 levels each, that is, 0, 32, 64, 96, 128, 160, 192, 224, and 255 respectively. These values of output levels are applied to the printer to print the patches.
Next, the tone level of each printed patch is measured by a colorimeter, for example. A correspondence relationship between input tone levels, supplied to the printer, and the output tone levels, obtained by the colorimeter, is obtained. Other output tone levels that correspond to input levels that are not actually supplied to the printer, are calculated by interpolating between the actually-measured output tone levels. Then, calibration data is determined that represents a correspondence relationship between all the 0-235 original tone levels, which can be supplied from an upper rank program for producing output tone levels of 0-255, and input tone levels, that should be supplied to the printer to reproduce the corresponding tones.
Afterward, in order to control the printer to actually print desired images, original tone levels supplied from the upper rank program are converted into input tone levels using the calibration data. The converted input tone levels are then supplied to this printer so that the printer can perform printing operation to produce a printed matter.
With this configuration, if output tone levels are measured from the printed matter, the tone levels will properly match the original tone levels, in the image data originally supplied from the upper rank program.
In the above-described conceivable color calibration operations, however, the tone levels of all the patches on the test chart have to be measured. It is noted that the total number of patches is equal to the product of the total number of ink colors and the total number of patches in each color. Because there are four rows of patches with nine patches in each row in the test chart of FIG. 1, then the tone levels of 36 patches have to be measured. This requires a considerable amount of time. It is therefore desirable to reduce the amount of time required for measuring tone levels of the patches.
Additionally, because color calibration operations take a considerable amount of time to complete, a user will possibly desire to start printing in the middle of color calibration preparing operations. However, until the tone levels of all the printed patches are measured, calibration data can not be prepared, so the user can not start printing.
In view of the above-described drawbacks, it is an objective of the present invention to overcome the above-described problems and to provide an improved tone characteristic data producing device that is capable of preparing tone characteristic data in a short period of time and that in capable of preparing tone characteristic data even if operations for measuring tone levels of patches on the test chart are stopped short part of the way through.
In order to attain the above and other objects, the present invention provides a tone characteristic data producing device for producing tone characteristic data of an image formation device, the tone characteristic data producing device, comprising an input unit that inputs data of a plurality of input levels to an image formation device, thereby controlling the image formation device to produce a plurality of tone patches; a measurement control unit that controls a tone measurement device to measure tone of at least two tone patches among the plurality of tone patches, thereby producing data of at least two output levels indicative of the measured tone of the at least two tone patches; a characteristic data production unit that produces tone characteristic data based on relationship between the at least two output levels and corresponding input levels; and a patch number control unit that controls the number of tone patches to be measured by the tone measurement device.
The input unit may preferably input a predetermined number of input levels, for each of a plurality of colors, to the image formation device, thereby controlling the image formation device to form the predetermined number of tone patches for each color, and may further input a single lowest input level for all the colors to the image formation device, thereby controlling the image formation device to form a single tone patch common to all the colors. The patch number control unit may control the measurement control unit to cause the measurement device to measure, for each color, the predetermined number of tone patches that correspond to the predetermined number of tone patches, thereby producing the predetermined number of output levels, and to measure the single one tone patch that commonly corresponds to the lowest input levels for all the colors, thereby producing a single common output level. In this case, the characteristic data production unit produces, for each color, tone characteristic data based on the predetermined number of input levels and the predetermined number of corresponding output levels and based on the lowest input levels and the single common output level.
Thus, is this case, the image formation devise, can form images using several coloring material. The coloring material is for providing color tone. Representative examples of the coloring material are ink, toner, and the like. Because an output level corresponding to the lowest input level can be measured by only a single measurement operation. Thus, the number of patches required to be measured is decreased, and thus, the total amounts of time required for the entire measurement operation can be reduced.
The tone characteristic data producing device may further include a memory storing a standard tone characteristic data. In this case, the measurement control unit includes a judgment unit that judges, for each tone patch, whether a shift, defined between the measured output level and a corresponding standard output level that is obtained based on the standard tone characteristic data, is within a predetermined range.
For example, the characteristic data production unit may store, in the memory, the tone characteristic data produced in each characteristic data producing operation. In this case, the measurement control unit retrieves, for a present characteristic data producing operation, a set of tone characteristic data that has been produced by the tone characteristic data production unit is the latest characteristics data producing operation as the standard tone characteristic data. Or, the standard tone characteristic data may be stored in the memory before the tone characteristic data producing device is shipped from a manufacturer.
The measurement control unit may further include a warning unit that issues a warning when the shift is judged to be out of the predetermined range. Or, the tone characteristic data production unit map include: an output level selecting unit that selects, when the shift obtained for one tone patch is judged to be out of the predetermined range, output levels that are obtained by two tone patches, whose corresponding input levels have values sandwiching an input level for the subject tone patch; and a calculating unit that calculates an output level for the subject tone patch by interpolating between the selected two output levels.
Thus, the system judges, for each tone patch, whether a shift, defined between the measured output level and a corresponding predicted output level that is obtained based on the standard tone characteristic data, is greater than a predetermined reference value. The standard tone characteristic data set has, for as input level of each tone patch, a value of an output level that will generally be outputted from the measurement device when the measurement device measures a tone patch obtained by the corresponding input level. Representative examples of the standard tone characteristic data include: a set of tone characteristic data that in produced in a latest characteristic data production operation, and a set of tone characteristic data prepared before the system is shipped from a manufacturer. That is, the standard tone characteristic data may be another set of tone characteristic data that is produced in a characteristic data production operation performed before the system is shipped from the manufacturer.
A reference value indicative of the predetermined range may be defined in terms of a difference or a ratio between the actually-obtained output level and the predicted output level. When the difference or ratio is not within the predetermined range (xc2x15 or xc2x15%, for example), it is judged that the shift is greater than the predetermined reference value. When the shift is judged to be greater than the reference value, the system may issue a warning. Or, the system may simply calculate an output level for the subject tone patch by interpolating between two output levels actually obtained by the measurement device for two tone patches, whose corresponding input levels have values that sandwich an input level for the subject tone patch.
The input unit may input a predetermined number of input levels to the image formation device, the predetermined number of input levels including a predetermined lowest input level and a predetermined highest input level, thereby causing the image formation device to form the predetermined number of tone patches. In this case, the patch number control unit controls the measurement control unit to cause corresponding to the predetermined lowest and highest input levels among the predetermined number of tone patches to produce output levels corresponding to at least the lowest and highest input levels, while allowing the measurement control unit to stop control of the measurement device to measure the tone patches after the measurement device measures the tone patches corresponding to the predetermined lowest and highest input levels. The characteristic data production unit produces the tone characteristic data by using the measured output levels and corresponding input levels and by interpolating between the measured output levels to calculate output levels for unmeasured patch.
For example, the input unit my input a predetermined xe2x80x9cnxe2x80x9d number of different input density levels to the image formation device, thereby controlling the image formation device to form the predetermined xe2x80x9cnxe2x80x9d number of tone patches corresponding to the xe2x80x9cnxe2x80x9d number of input density levels, wherein xe2x80x9cnxe2x80x9d is an integer greater than or equal to three (3). The measurement control unit may control the tone measurement device to successively measure the xe2x80x9cnxe2x80x9d number of tone patches from a first measurement operation to a n-th measurement operation in an order that either one of the tone patches for the highest and lowest input levels be measured in a xe2x80x9cmxe2x80x9d-th measurement operation among the total xe2x80x9cnxe2x80x9d tone patches, where m is an integer greater than or equal to two (2) and smaller than n, and that the other one of the tone patches be measured in a measuring operation conducted prior to the m-th measuring operation. The patch number control unit controls the measurement control unit to cause the measurement device to perform the first to m-th measurement operation, while allowing the measurement control unit to stop control of the measurement after the measurement device performs the m-th measurement operation.
When the m-th measuring operation is completed, measurement of tone patches that are formed based on the highest and lowest input levels are completed. All of the patches not yet measured are formed based on input levels that are greater than the lowest input level and smaller than the highest input level. Though output levels for the not-yet-measured patches can be measured, values near to the output levels for those patches can be calculated by simply interpolating output levels for m-number of patches obtained during the first through m-th measuring operations. It therefore becomes unnecessary to measure the not-yet-measured tone patches. Accordingly, tone characteristic data can be produced based on relationship between the measured output levels and the input levels for the measured tone patches and based on relationship between the calculated values and the input levels for the unmeasured tone patches.
It becomes optional to or not to continue performing the (m+1)-th through n-th measuring operations. It is possible to immediately complete tone characteristic data after completing the first through m-th measuring operations.
The value m be selected as long as the value m is greater than or equal to two (2) and smaller than n. It is possible to immediately stop the measurement as the value xe2x80x9cmxe2x80x9d decreases. When the number xe2x80x9cnxe2x80x9d is relatively large, however, it will possibly be difficult to produce accurate tone characteristic data by interpolating the output levels corresponding to the highest and lowest input levels only. In such a case, xe2x80x9cmxe2x80x9d should be set to some great value. It becomes possible to prevent production of too inaccurate tone characteristic data due to excessively immediately stop of measurement.
For example, the input unit may successively input the n number of input levels in a predetermined order through first through n-th input operations so that the image formation device forms the n tone patches including first through n-th tone patches in the same order and so that the tone measurement device measures at least two tone patches among the a tone patches in the same order, the input unit inputting either one of the highest and lowest input levels in the first input operation and inputting the other one of the highest and lowest input levels in the second input operation, thereby allowing the image formation device to produce each of first and second patches based on either one of the highest and lowest input levels, the input unit inputting input levels for producing (2k+2)-th through (2k+1+1)-th tone patches so that each of the input levels has a value between a corresponding adjacent two input levels for the first through (2k+1)-th tone patches when the input levels for the first through (2k+1)-th tone patches are arranged in an order of their magnitudes, where k is an integer greater than or equal to zero (0).
For example, in order to produce ten patches based on ten input levels xe2x80x9c0-9,xe2x80x9d the highest and lowest input levels xe2x80x9c9xe2x80x9d and xe2x80x9c0xe2x80x9d are selected as first and second input levels or as second and first input levels to be inputted to the image formation device. That is, the first and second patches map be produced based on input levels xe2x80x9c0xe2x80x9d and xe2x80x9c9xe2x80x9d or xe2x80x9c9xe2x80x9d and xe2x80x9c0xe2x80x9d. Now, it is assumed that the input unit inputs xe2x80x9c0xe2x80x9d and xe2x80x9c9xe2x80x9d as first and second input levels in this order. The third patch is produced by inputting, as a third input level, a value of either one of values that are located between the first and second input levels xe2x80x9c0xe2x80x9d and xe2x80x9c0xe2x80x9d when the first and second input levels xe2x80x9c0xe2x80x9d and xe2x80x9c9xe2x80x9d are arranged in the order of their magnitudes. In this example, therefore, a value of either one of the values xe2x80x9c1xe2x80x9d through xe2x80x9c8xe2x80x9d is selected. It is preferable to select a value that is positioned at a substantially centered location when those values of xe2x80x9c1xe2x80x9d through xe2x80x9c8xe2x80x9d are arranged in the order of their magnitudes. Accordingly, it is preferable to select xe2x80x9c4xe2x80x9d or xe2x80x9c5xe2x80x9d. It is now assumed that xe2x80x9c4xe2x80x9d is selected as the third input level and therefore that the input unit inputs the input level xe2x80x9c0xe2x80x9d xe2x80x9c9xe2x80x9d xe2x80x9c4xe2x80x9d in this order.
In order to produce fourth and fifth patches, the input unit inputs, as fourth and fifth input levels, values that are located between respective two adjacent values among the values of xe2x80x9c0,xe2x80x9d xe2x80x9c4xe2x80x9d and xe2x80x9c9xe2x80x9d when they are arranged in the order of their magnitudes. That is, either one of values xe2x80x9c1xe2x80x9d through xe2x80x9c3xe2x80x9d that are located between xe2x80x9c0xe2x80x9d and xe2x80x9c4xe2x80x9d and either one of values xe2x80x9c5xe2x80x9d through xe2x80x9c8xe2x80x9d that are located between xe2x80x9c4xe2x80x9d and xe2x80x9c9xe2x80x9d are selected as fourth and fifth input levels, respectively. Also in this case, it is preferable to select a value that is located contend in the values xe2x80x9c1xe2x80x9d through xe2x80x9c3xe2x80x9d. Therefore, it is preferable to select xe2x80x9c2xe2x80x9d. Similarly, it is preferable to select a value that is located contained in the values xe2x80x9c5xe2x80x9d through xe2x80x9c8xe2x80x9d. In this case, it is preferable to select xe2x80x9c6xe2x80x9d or xe2x80x9d7xe2x80x9d. It is now assumed that xe2x80x9c2xe2x80x9d and xe2x80x9c6xe2x80x9d are selected as the fourth and fifth input levels. It is noted that either of the selected values xe2x80x9c2xe2x80x9d and xe2x80x9c6xe2x80x9d can be set as the fourth input level and the other one be set as the fifth input level. Accordingly, the input unit may input the input levels xe2x80x9c0xe2x80x9d xe2x80x9c9xe2x80x9d xe2x80x9c4xe2x80x9d xe2x80x9c2xe2x80x9d and xe2x80x9c6xe2x80x9d in this order, or alternatively may input the input levels xe2x80x9c0xe2x80x9d xe2x80x9c9xe2x80x9d xe2x80x9c4xe2x80x9d 6xe2x80x9d and xe2x80x9c2xe2x80x9d in this order. It is now assumed that the input unit inputs the input levels xe2x80x9c0xe2x80x9d xe2x80x9c9xe2x80x9d xe2x80x9c4xe2x80x9d xe2x80x9c2xe2x80x9d and xe2x80x9c6xe2x80x9d in this order.
In the similar manner as described above, in order to produce sixth through ninth patches, the input unit has to input, as sixth through ninth input levels, values that are located between respective two adjacent values among the values of xe2x80x9c0,xe2x80x9d xe2x80x9c4,xe2x80x9d xe2x80x9c9,xe2x80x9d 2,xe2x80x9d and xe2x80x9c6xe2x80x9d when they are arranged in the order of their magnitudes, that it, xe2x80x9c0, 2, 4, 6, 9xe2x80x9d. As a result, xe2x80x9c1xe2x80x9d, xe2x80x9c3xe2x80x9d, xe2x80x9c5xe2x80x9d, and xe2x80x9c7xe2x80x9d are selected as sixth through ninth input levels. xe2x80x9c8xe2x80x9d may be selected instead of xe2x80x9c7xe2x80x9d for the ninth input level. It is now assumed that the xe2x80x9c7xe2x80x9d is selected for the ninth input level. Either one of the thus selected four values may be used as one of the sixth through ninth input levels. For example, the input unit may input xe2x80x9c0, 9, 4, 2, 6, 1, 3, 5, 7xe2x80x9d in this order. The remaining xe2x80x9c8xe2x80x9d selected for the last or tenth input level. In total, the input unit inputs xe2x80x9c0, 9, 4, 2, 6, 1, 3, 5, 7, and xe2x80x9c8xe2x80x9d in this order.
Accordingly, any time when the measurement is stopped after measurement of the third patch, input levels for already-measured patches are distributed widely uniformly in the entire range of the input levels. Comparing with the case where input levels for already-measured patches are located collectively within some numerical range, output levels calculated by interpolating between the already-measured output levels can be produced accurately over the entire range for the output levels.
For example, the input unit may input, for each of several colors, the n number of input levels to the image formation device, thereby allowing the image formation device to produce the n number of tone patches for each color, the measurement control unit controlling the tone measurement device to measure, for each color, at least first through m-th tone patches, the characteristic data producing unit producing tone characteristic data, for each color, based on the measured tone patches of the corresponding color.
Accordingly, even when the relationship between the input levels and the output levels are different for each color, tone characteristic data can be produced for each color.
Alternatively, the input unit may input, for a single color, the n number or input levels to the image formation device, thereby allowing the image formation device to produce the n number of tone patches for the single color, the measurement control unit controlling the tone measurement device to measure, for the single color, at least first through m-th tone patches, the characteristic data producing unit producing tone characteristic data, for the single color, based on the measured tone patches. Thus, the system can provide tone characteristic data for a single color component.
The patch number control unit may include a designation unit that designates a desired number of patches to produce. In this case, the input unit inputs the designated number of input levels to the image formation device, thereby producing the designated number of tone patches. The measurement control unit controls the measurement device to measure the designated number of tone patches, thereby producing the designated number of output levels. The characteristic data production unit produces the tone characteristic data based on the designated number of input levels and the corresponding designated number of output levels.
The device may further include a memory storing a plurality of sets of test data, each test data set including the plurality of input levels to be inputted to the image formation device; and a selecting unit that selects one set of test data, produces the designated number of input levels based on the selected test data set, and inputs the produced input levels to the image formation device, thereby allowing the image formation device to produce the plurality of tone patches. In this case, the plurality of note of test data may correspond to a plurality of different tone measurement devices or to a plurality of different, image forming conditions used at the image formation device.
In this case, the device stores a plurality of sets of test data that will control the image formation device to form a plurality of test chart. When one set of test data is selected, the system produces image formation data for printing the test chart based on the selected test data set, and outputs the produced image formation data to the image formation device. Thus, the plurality of sets of test data are stored in a selectable manner. Accordingly, when a desired set of test data is selected from the plurality of sets of test data, the image formation device is controlled to form a test chart based on the selected test data set. For example, the user can select one set of test data that corresponds to a colorimeter that he/she uses and to an actual image formation condition set in the image formation device. The image formation device is controlled to form a test chart based on the selected test data. The user can measure the test chart using his/her own colorimeter. Additionally, tone characteristic data corresponding to the user""s desired image formation condition can be properly set. Thus, the tone characteristic data can be highly efficiently set.
Especially when the device stores the plurality of sets of test data in correspondence with a plurality of colorimeters, the user can select one test data set that corresponds to his/her own colorimeter. Thus, a test chart optimum to be measured by the user""s colorimeter can be formed by the image formation device.
On the other hand, when the device stores the plurality of sets of test data in correspondence with a plurality of image formation conditions that can be switchingly set to the image formation device, the user can select one test data set that corresponds to image formation condition that he/she sets for the image formation device. Then, a test chart corresponding to the user""s selected test data is formed by the image formation device. Based on color measurement data obtained on the test chart, it is possible to set tone characteristic data optimum to the user""s desired image formation condition. Accordingly, the tone characteristic producing device is convenient to use. Tone characteristic data obtained by the tone characteristic producing device is optimum for the image formation device to form images.
Each set of test data is comprised from a plurality of types of data that indicates a shape of a test chart, per se., a shape of each of a plurality of patches to be formed on the test chart, how the patches should be arranged, colors of the patches, and etc.
Because the user can designate the number of patches desired to be provided on the test chart, even when using a manual colorimeter, the measurement can be completed within a short period of time. Additionally, by designating the number of patches, it becomes possible to automatically determine tones to be provided on the respective patches using the selected test data set. It may be possible, for example, to uniformly divide the 256 tones of levels for each color by the designated number of patches to determine tones to be provided vat each color patch. Accordingly, it is possible to uniformly distribute the entire 256 tone of each color into the color patches on the test chart. By using the test chart provided with the color patches, it is possible to produce calibration data substantially accurately. It is therefore possible to stably form tonal images that faithfully reproduce image data.
It is noted that the tone characteristic setting device may preferably be incorporated, into a computer system, together with an image processing portion for converting original tone data into input tone data to be supplied to the image formation device. The computer system is comprised from a personal computer, a monitor, a key board, a mouse, and etc. In this case, the monitor is used to display an indication to urge the user to select a desired colorimeter, and the keyboard or the mouser is used to select and input the user""s selection. It is possible to successively perform all the processes including: selection of parameters, calculations, output of test image data, input of color measured results, end calculation of tone characteristic data.
The tone characteristic device can be incorporated into an image formation device such as a printer or a display. In this case, the selection unit such as a monitor, a selecting button, and the like has to be incorporated into the image formation device. When the tone characteristic device is incorporated into the image formation device, a test chart can in produced immediately.
The tone characteristic data producing system can be constructed as a system for exclusively producing tone characteristic data. However, the system can be constructed from a general use computer system. In this case, a data recording odium storing a tone characteristic data production program is provided, and the program in retrieved from the data recording medium and installed into the computer system.
That is, the present invention provides a data recording medium, storing a tone characteristic data producing program for being read by a computer system to control the computer system to produce tone characteristic data of an image formation device, the program comprising: a program of inputting data of a plurality of input levels to an image formation device, thereby controlling the image formation device to produce a plurality of tone patches; a program of controlling a tone measurement device to measure tone of at least two tone patches among the plurality of tone patches, thereby producing data of at least two output levels indicative of the measured tone of the at least two tone patches; a program of producing tone characteristic data based on relationship between the at least two output levels and corresponding input levels; and a program of controlling the number of tone patches to be measured.
Representative examples of the data recording medium are: a magnetic data recording medium, such as a flexible disk, from which data can be read magnetically; and an optically data recording medium, such as a CD-ROM from which data can be read optically, and the like. Any data recording medium that can be used in a computer system can be used.